Preparation Of Cyclodextrin/MnO₂ Materials And Their Performance In Removal Of Benzene Series

Groundwater occupies 30%of the earth's total freshwater resourcesand is an important source of domestic water.However,the problem of groundwater pollution in my country is now serious.In the process of groundwater testing in more than 200 cities across the country,it was found that the proportion of poor and extremely poor water quality exceeded 59.6%.This is mainly caused by municipal waste landfills,substandard industrial"three wastes"emissions,agricultural fertilization and excessive pesticide spraying.Among them,benzene series?BTEX?are a kind of common groundwater pollutants.Benzene series are aromatic hydrocarbon compounds,which are highly volatile,flammable,and toxic substances,which have serious harm to human health.In view of the difficulty in percolation of groundwater itself and poor exchange,it is difficult to return to the original state through natural purification after being polluted.Therefore,once the groundwater is polluted,a lot of manpower and material resources are often needed to repair the polluted groundwater.Permeable reaction wall is a common new type of groundwater remediation and treatment technology.By installing a specific reaction medium vertically in the downstream of the contaminated groundwater system that needs to be treated,it blocks the pollution zone and prevents the continuous flow of pollutants.The target pollutants are removed or transformed into a form acceptable to natural water bodies.However,the reaction medium packing suffers from regeneration and difficulty in degrading pollutants.This research hopes to prepare cyclodextrin composite materials with high adsorption performance and combine with potassium permanganate oxidation to achieve the purpose of adsorption and degradation of pollutants in one,in order to expand the application of cyclodextrin materials in permeable reaction walls.In this study,?-cyclodextrin polymer was prepared by inverse emulsion polymerization,then the?-cyclodextrin polymer was oxidized by potassium permanganate?KMnO₄?to prepare microsphere?-cyclodextrin/manganese dioxide composite materials with the mesoporous structure.Among them,Mn is embedded in the?-cyclodextrin polymer matrix in the form of MnO_2,and the pores are not blocked.Compared with?-cyclodextrin polymers,composite materials have larger pore size,reduced pore volume and specific surface area,uniform swelling particle size distribution,and better sedimentation and swelling performance.The study found that the?-cyclodextrin/manganese dioxide composite material has good adsorption performance for phenol,toluene,ethylbenzene,and p-xylene in simulated groundwater,and the adsorption removal rate is 49%-82%.The influence of groundwater environmental factors such as water pH,ammonia nitrogen concentration and sulfide concentration on the adsorption performance was investigated.The results show that the concentration of ammonia nitrogen and sulfide in the water has no obvious effect on the adsorption performance.The dosage of composite materials and the pH of the water are important factors that affect the adsorption performance.The adsorption removal rate increases with the increase of the composite material dosage,and decreases with the increase of the pH of the water.The?-cyclodextrin/manganese dioxide composite material is oxidized by KMnO₄ after adsorbing benzene series,and the benzene series attached to the composite material are removed,and the removal rate is 87%-93%.At the same time,the influence of some groundwater environmental factors such as water pH,ammonia nitrogen concentration and sulfide concentration on the effect of KMnO₄ oxidation to remove the benzene series attached to the composite material was investigated.The results show that the concentration of ammonia nitrogen and sulfide in the water body has no significant effect on the removal of benzene series by KMnO₄ oxidation.The KMnO₄ concentration and water pH are important factors that affect the removal of benzene series by oxidation.The removal rate increases with the increase of KMnO₄ concentration,and decreases first and then increases with the increase of water pH?the removal rate of phenol keeps increasing?.Regeneration experiments show that the composite material can still maintain the original pollutant removal effect after 5cycles of oxidation and utilization,and has a good engineering application prospect.